Gastric Cancer Gastric cancer is the predominant cancer in Linqu County, Shandong Province, China, where the Biostatistics Branch is conducting an intervention trial and studies of gastric cancer etiology. Evaluation of the impact of repeated endoscopic screens (1989, 1994, and 1999) found no reduction in GC mortality in this high-risk Linqu population. A recent cross-sectional study among 3,288 adults in Linqu County found that Helicobacter pylori (H. pylori) seroprevalence was elevated for: infrequent hand washing before meals (OR=1.7, 95%CI=1.0-3.0), sharing a bed with more than two people (OR=2.3, 95%CI=1.3-4.2), washing/bathing in a pond or ditch (OR=1.5, 95%CI=1.0-2.4), and medium (OR=1.6, 95%CI=1.3-2.0) and low (OR=2.3, 95%CI=1.9-2.9) compared to high village education level, and reduced for never being married or being divorced (OR=0.4, 95%CI=0.2-1.0). These findings suggest that person-to-person transmission is the most plausible route of H. pylori infection in this rural Chinese population, but waterborne exposures deserve further investigation. The prevalence of H. pylori in general and CagA+ strains in particular as determined by 13C-UBT was compared among children aged 3-12 years in Shandong Province, China in areas at high (98 children in Linqu County) and low risk (101 children in Cangshan County) of GC . The percent of H. pylori-positive children was nearly three times higher among children in Linqu (69.4%) than in Cangshan (28.7%) and may contribute to the large differential in GC rates in these neighboring populations. Among children positive for 13C-UBT, the proportion of CagA+ strains was 88.5% in Linqu and 81.3% in Cangshan. Further studies in adults in these two populations revealed that only 13.5% of subjects had advanced precancerous gastric lesions (intestinal metaplasia or dysplasia) in Cangshan compared to 45.1% in Linqu. H. pylori positivity assessed both by whole cell enzyme-linked immunosorbent assays (ELISA) and by antibodies to CagA were predictive of advanced precancerous gastric lesions, but those factors did not account for the large difference in the prevalence of advanced precancerous gastric lesions between these two regions. Colon Cancer There was little evidence of an association between intake of fruits or vegetables and risk of colorectal cancer in an analysis of 477 colorectal cancer cases diagnosed among 45,486 women who completed a 62-item NCI/Block food-frequency questionnaire as part of the Breast Cancer Detection Demonstration Project Follow-up Study. Hepatocellular Carcinoma An extensive laboratory analysis of sera from 181 incident cases of hepatocellular carcinoma in Qidong, Jiangsu Province, China revealed evidence of hepatitis B infection in every case. Only six cases were co-infected with hepatitis C. The mutation 249-ser-p53 was found in 54% of these incident cases, and in none of 42 cases from Beijing, where exposure to aflatoxin is thought to be much less. It is concluded from these and other data that exposure to hepatitis B is the dominant factor in hepatocarcinogenesis in Qidong and that it probably sensitizes subjects to the effects of aflatoxin, which together with hepatitis B, leads to the 249-ser-p53 mutation.